Correct, except the worst case maximum for disk space is three times. --wunder
On Apr 10, 2013, at 6:04 AM, Erick Erickson wrote: > You're mixing up disk and RAM requirements when you talk > about having twice the disk size. Solr does _NOT_ require > twice the index size of RAM to optimize, it requires twice > the size on _DISK_. > > In terms of RAM requirements, you need to create an index, > run realistic queries at the installation and measure. > > Best > Erick > > On Tue, Apr 9, 2013 at 10:32 PM, bigjust <bigj...@lambdaphil.es> wrote: >> >> >> >>>> On 4/9/2013 7:03 PM, Furkan KAMACI wrote: >>>>> These are really good metrics for me: >>>>> You say that RAM size should be at least index size, and it is >>>>> better to have a RAM size twice the index size (because of worst >>>>> case scenario). >>>>> On the other hand let's assume that I have a RAM size that is >>>>> bigger than twice of indexes at machine. Can Solr use that extra >>>>> RAM or is it a approximately maximum limit (to have twice size of >>>>> indexes at machine)? >>>> What we have been discussing is the OS cache, which is memory that >>>> is not used by programs. The OS uses that memory to make everything >>>> run faster. The OS will instantly give that memory up if a program >>>> requests it. >>>> Solr is a java program, and java uses memory a little differently, >>>> so Solr most likely will NOT use more memory when it is available. >>>> In a "normal" directly executable program, memory can be allocated >>>> at any time, and given back to the system at any time. >>>> With Java, you tell it the maximum amount of memory the program is >>>> ever allowed to use. Because of how memory is used inside Java, >>>> most long-running Java programs (like Solr) will allocate up to the >>>> configured maximum even if they don't really need that much memory. >>>> Most Java virtual machines will never give the memory back to the >>>> system even if it is not required. >>>> Thanks, Shawn >>>> >>>> >> Furkan KAMACI <furkankam...@gmail.com> writes: >> >>> I am sorry but you said: >>> >>> *you need enough free RAM for the OS to cache the maximum amount of >>> disk space all your indexes will ever use* >>> >>> I have made an assumption my indexes at my machine. Let's assume that >>> it is 5 GB. So it is better to have at least 5 GB RAM? OK, Solr will >>> use RAM up to how much I define it as a Java processes. When we think >>> about the indexes at storage and caching them at RAM by OS, is that >>> what you talk about: having more than 5 GB - or - 10 GB RAM for my >>> machine? >>> >>> 2013/4/10 Shawn Heisey <s...@elyograg.org> >>> >> >> 10 GB. Because when Solr shuffles the data around, it could use up to >> twice the size of the index in order to optimize the index on disk. >> >> -- Justin -- Walter Underwood wun...@wunderwood.org
